The "leave the worries at home" part says it all. The more relaxed you are, the better you'll shoot. Plan to shoot your average. The point of practice is to raise your average, not get psyched up for a big match. Consider the So Nats practice for your NEXT big match. (All matches are practice.) I personally plan to taper off on the practice the last week.
Get there early, try the airguns, practice the smallbore and by all means get into a team for the Coonass Team Shoot Friday afternoon. It really breaks the ice. Speaking of which, bring an ice chest, sunscreen and a light raincoat just in case. That's about it. Plan to laugh a lot. Find the Benton Gun Club tent and introduce yourself. We'll let you meet Chicken George.
Watch out for Culpepper.